1. Technical Field
The present invention is directed to a gemstone setting and a method for molding the gemstone setting and, more particularly, to gemstone settings with seats molded directly into the settings and a method for molding seats into gemstone settings using metal molds.
2. Related Art
A variety of gemstone settings (hereinafter xe2x80x9csettingxe2x80x9d or xe2x80x9csettingsxe2x80x9d) are used in the jewelry industry. The selection of settings is usually made to enhance the beauty of a gemstone (hereinafter xe2x80x9cgemxe2x80x9d). Settings may be hand-carved, molded, or stamped, and may include prongs that frictionally maintain a gem in the setting. Stamped settings are generally less attractive, and less malleable than those formed from other processes due to the deformation of metal inherent in the stamping process.
A typical molded setting 10 is shown for illustrative purposes only in FIG. 1. Setting 10 includes a base indicated generally at 12 having a perimeter 14 from which a plurality of prongs 16 having an inner face 22 extend upwardly and slightly outwardly, terminating at upper prong surface 17. Setting 10 also includes a band 18 approximately midway between the perimeter 14 of base 12 and upper prong surface 17.
In some instances, inner face 22 of prongs 16 may include a xe2x80x9cseatxe2x80x9d on which a gem may be fitted or into which it xe2x80x9csits.xe2x80x9d Seats may be hand-carved, stamped, or molded directly into the inner face of the prongs of a setting at the upper end of the prongs. FIG. 2 illustrates such a setting 10a, which includes all of the elements of setting 10, and additionally includes a hand-carved seat 24 formed at upper end 20 of prong 16 on the inner surface 22 of each prong 16. An expanded side view of seat 24 is illustrated in FIG. 3, showing a portion 22a of inner surface 22 of prong 16 remaining exposed above seat 24 after hand-carving.
A side view of a typical gem 30 is shown in FIG. 4 for illustrative purposes only. Gem 30 includes a table 32, a crown 34, a culet 36, a pavilion 38, and a girdle 40.
FIG. 5 shows a perspective view of a set gem 50 using, for example, gem 30 and setting 10a. As shown, gem 30 is xe2x80x9csetxe2x80x9d by positioning girdle 40 in seats 24 and folding upper ends 20a of prongs 16 downwardly toward crown 34 of gem 30. The folding process requires the exertion of a great deal of force in order to ensure that surface 22a of prong 16 contacts crown 34, as shown in side view in FIG. 6. If excessive force is exerted during this process, the gem may shatter. Generally, the intersection of crown 34 and girdle 40 at line L1, and the intersection of girdle 40 with pavilion 38 at line L2, are the points or lines of intersection at which the seat directly contacts the gem 30, due to the arcuate shape of hand-carved seats.
Regardless of the method used to form the seats, it is important for aesthetic reasons to ensure that the size and placement of the seats remains substantially the same on each prong of a setting. If the gem is not level with respect to the base of the setting, it will appear crooked to the naked eye. In addition, if the placement of the seats on the prongs of a setting varies, the length of the portion of the prongs (i.e. 22a) that is folded onto crown 34 will vary. Both of these are undesirable for aesthetic reasons and consequently for economic reasons.
Hand-carving seats require a great degree of skill and precision on the part of the jewelry maker to ensure that the size and placement of the seats remains substantially the same on each prong. Hand-carved seats have a generally arcuate shape, as shown in FIG. 3. The arcuate shape of hand-carved seats sometimes may be disadvantageous when attempting to xe2x80x9csetxe2x80x9d a stone in a setting if the carving has penetrated too deeply into the interior face of the prong, or if the placement of the seat on each prong varies.
One method of addressing the foregoing problems involves molding seats directly into the prongs of a setting using what is known as the xe2x80x9crubber molding process.xe2x80x9d The rubber molding process (RMP) involves forming a master setting using conventional means such as would be known to jewelry makers. The master setting is then encased in rubber, and the rubber is allowed to harden. The rubber mold is then split in half, resulting in two complementary mold halves. An exemplary rubber mold halve 60 is illustrated in side view in FIG. 7. Rubber mold 60 includes a parting surface 62, with a relief pattern formed in mold halve 60, fluidly connected to a sprue 64 and gate 66 for receiving fluid material, each which are known to those of skill in the art. The relief pattern includes a plurality of fluidly connected channels or partial channels corresponding to the structure of the desired setting. For example, channel 68 corresponds to base 14, channel 70 corresponds to band 18, and channels 72 correspond to prongs 16.
Because the rubber can flow around and encase the master setting, the rubber mold process can reproduce all the features of the master setting, including the interior surface of the setting. Section 74 of mold 62 includes a relief pattern of the inner surface of the desired setting. For example, section 74 includes grooves 76 corresponding to the inner surface 22 of setting 10, 10a, as well as surface 78 corresponding to hand-carved seat 24. Thus, the relief pattern also represents the inner surface 22 of prongs 16 of setting 10a, including seats 24.
When the two complementary rubber mold halves are assembled, for example, by clamping, wax may be injected into the assembled rubber mold to form a wax copy of the master setting. The wax copy may be removed from the mold by disassembling the two rubber mold halves. The wax copy of the master setting may then be used to form a precious metal setting.
The remainder of the rubber molding process involves a xe2x80x9clost corexe2x80x9d process which is well know to those of ordinary skill in the art. The lost core plaster method involves casting the wax copy or copies in plaster, heating the plaster above the point at which the wax will decompose or carbonize, and injecting molten metal, typically a precious metal, into the plaster. After the metal has hardened, the plaster casting may be shattered to allow removal of the precious metal copy of the master setting.
Thus, if the master setting includes seats, the seats will be reproduced using the rubber molding process. The rubber molding process may be disadvantageous because the flexibility of the rubber mold makes it easy to slightly misalign or distort the mold halves when assembling the mold and during the molding process. This makes it difficult for the jewelry maker to ensure that the size and placement of the seats remains substantially the same on each prong and to maintain reproducibility between settings formed in this manner. Thus, for example, although it is possible to mold seats directly into settings using the rubber mold process, such seats may be at different positions on each of the prongs, resulting in irregularities in the position of the gemstones. In addition, the dimensional accuracy of the settings produced by this method are less than what is desirable due to the number of iterations required to obtain the desired precious metal copy of the original master, i.e. the precious metal copy is a copy of a wax copy, which in turn is a copy of the master setting. Each subsequent copying step reduces the overall accuracy of the final part in comparison to the master setting.
One attempt to overcome the foregoing problems with the rubber molding process involves using metal molds rather than rubber molds. The metal molding process provides greatly improved reproducibility and accuracy of the final setting in comparison to the rubber molding process. However, because metal molds must be machined, it is impossible to provide two mold halves that include a relief pattern of the interior and exterior of the desired setting. By way of explanation, a typical metal molding process now will be explained with reference to FIGS. 8-15. FIG. 8 shows a perspective view of a mold 100 for forming a setting using metal molds. Mold 100 includes two substantially symmetrical mold halves 100a,b, each having a top surface 102a,b. Preferably, each mold halve 100a,b may be machined from a metal such as brass, using a CAD image of the desired mold. Thus, it can be seen that the metal molding process does not require the formation of a master setting, as does the rubber molding process. This increases the dimensional accuracy of the final settings because fewer copying iterations are required than with the rubber molding process.
As shown in FIG. 9, which is an expanded view of mold 100, each brass mold halve 100a,b includes a parting surface 104a,b. A substantially frustoconical depression having a surface indicated generally at 106a,b is machined in each mold halve 100a,b, and is fluidly connected to a sprue 164a,b and a gate 166a,b for receiving material, each which are known to those of skill in the art. Each surface 106a,b includes a relief pattern of fluidly connected grooves corresponding to the outer surface of the structure of the desired setting. For example, grooves 114a,b correspond to base 14, grooves 118a,b correspond to band 18, and grooves 116a,b correspond to prongs 16. Unlike the rubber molding process, it is not possible to machine molds that include a relief pattern of the interior of the desired master setting. For example, inner surface 22 of prongs 16 cannot be machined in mold halves 100a,b. 
To overcome this problem, a xe2x80x9ccore pinxe2x80x9d is used in conjunction with mold 100. The core pin is formed by pressing a soft metal into mold 100. As shown in FIG. 10, which illustrates core pin 180 after pressing the soft metal into mold 100, the resulting core pin 180 includes a handle portion 182 and a frustoconical pin portion indicated generally at 184. As best shown in FIG. 1, an outer surface 106p of the frustoconical pin portions 184 includes a plurality of protrusions that correspond to the grooves of the relief pattern of mold 100a. For example, protrusions 118p corresponds to grooves 118a,b, protrusions 114p corresponds to grooves 114a,b, and protrusions 116p correspond to grooves 116a,b. Protrusions 114p, 116p, and 118p are filed away using, for example, a hand file, in order to obtain the core pin 180 shown in FIG. 12, having a substantially smooth exterior surface indicated generally at 106.
After removal of projections 114p, 116p, and 118p, core pin 180 has a substantially smooth exterior surface 106 that mates with the frustoconical interior surface 106a,b of mold 100. Thus, when core pin 180 is engaged with mold 100, the regions of core pin 180 from which material was removed define a channel corresponding to the structure of the desired setting. Plastic then may be injected into the mold through the sprue and gate of the mold, as is known in the art. After the plastic has solidified, a plastic copy of the desired master setting may be removed, as shown in FIGS. 13-14, which illustrate an exemplary setting 10 resulting from such a molding process.
Thereafter, the plastic copy 10 of the desired master gemstone setting is cast in plaster and heated to a temperature at which the plastic will melt or carbonize. A molten precious metal then may be introduced into the plaster casting, and upon cooling, the plaster may be cracked to allow removal of the precious metal setting.
Because metal molds are rigid, and less likely to deform during the molding process, the metal molding process provides accurate dimensional reproducibility. However, the metal molding process may be disadvantageous because the tooling required to make the brass mold and the core pin mold is expensive, the labor involved in filing the protrusions from the core pin mold is time consuming and critical, and it is not possible to mold seats directly into the gemstone settings. Thus, the seats must be hand carved into the prongs, which requires a great deal of skill, is labor-intensive, and therefore expensive.
Another attempt to overcome the foregoing problems is disclosed in U.S. Pat. No. 3,601,178 to Marticorena, which discloses a method for forming a unitary ring and gemstone setting using a rubber molding process.
Selective Laser Sintering (SLS) may be used to form molds for complex three dimensional objects that cannot otherwise be formed by machining metal or metal alloys. However, SLS and other related methods are extremely expensive.
Thus, there remains a need in the art for an improved setting and a method for making the settings.
The present disclosure is directed to a method for molding a gemstone setting having a plurality of prongs, using a metal mold. The method involves machining a first metal core pin mold, pressing a soft metal into the first core pin mold to obtain a core pin, and inserting the core pin into a second metal mold. A fluid non-metal material then may be injected into the second metal mold. The non-metal material may be allowed to harden and may be removed from the second mold to obtain a non-metal setting having a unitary seat disposed on the inner surface of each prong of the setting. The distance between the seat and a base of the setting and the distance between the seat and an end of each prong is substantially the same on each prong.
The method may also involve casting the non-metal setting in plaster, removing the non-metal setting from the plaster to form a plaster mold, introducing a molten metal into the plaster mold, and allowing the molten metal to harden. This allows the removal a metal setting from the plaster mold to obtain a metal setting having a unitary seat disposed on the inner surface of each prong of the setting.
The prong of the setting may include a substantially smooth inner surface interrupted by a step, and the step forms at least a portion of the seat.
The core pin mold may include an interior surface defined by a frustum, with the interior surface of the frustum including a step disposed a predetermined distance from the base of the frustum.
The step of pressing a soft metal into the core pin mold involves forming a core pin having a handle portion and a frustum extending from the handle portion. The frustum has an outer surface interrupted by a continuous step disposed about the frustum. The step is disposed a predetermined distance from the base of the frustum.
In some embodiments, the step may be perpendicular to the outer surface of the frustum.
The disclosure is also directed to a molded gemstone setting having a plurality of prongs in which a gemstone having a girdle and a crown is disposed. The gemstone setting includes a base having a perimeter and a plurality of prongs extending upwardly from the perimeter of the base. Each prong has an upper surface, a substantially flat inner surface, and a substantially arcuate outer surface. A seat defined at least partially by a step may be disposed on the inner surface of each prong between the base and the upper surface of each prong, the thickness of each prong. The step may be substantially the distance from the step to the upper surface of each prong. The seat may be constructed and arranged to position the girdle of the gemstone substantially parallel to the base of the gemstone setting. The inner surface of the prongs above the step may be constructed and arranged to substantially conform to the girdle and crown of the gemstone when the prongs of the setting are folded toward the crown of the gemstone.